1. Field of the Invention
This invention relates to a method of making electrically conducting acrylic and acrylic-series fibers.
2. Description of the Prior Art
Methods for imparting electrical conductivity to synthetic polymeric fibers are known in the art. These methods include, for example, the plating of the surface of fibers with a metal and the kneading of a metal into a polymer which is then spun into a yarn.
U.S. Pat. Nos. 3,014,818 and 4,122,143 disclose methods of producing electrically conductive products by the reduction of a copper compound to metallic copper. In U.S. Pat. No. 3,014,818, an electrically conductive fibrous material is produced by soaking the fiber, such as cotton or acrylic fibers, in a bath comprising a reducible salt of nickel, cobalt, copper or iron. The fiber is then subjected to a reducing treatment to obtain free metal particles which are dispersed through the interior of the fiber. Sodium borohydride and hydroxylamine are disclosed as satisfactory reducing agents. According to U.S. Pat. No. 4,122,143, cured products are obtained by reducing copper simultaneously with the curing of a resin. The imparting of electrical conductivity to an existing fiber is not disclosed.
These methods suffer from various disadvantages including the requirement of complicated treatment processes, the requirement of high-grade techniques of manufacture and the obtaining of fibers which do not have good color, touch and other physical characteristics.
The present inventors developed a method for producing electrically conductive acrylic and acrylic-series fibers which avoids the disadvantages of the prior art methods. The acrylic or acrylic-series fibers are heat-treated in a bath containing monovalent copper ions so that the fibers adsorb the monovalent copper ions. The fibers are then heat-treated with a sulfur-containing compound to convert the adsorbed monovalent copper ions into cuprous sulfide or cupric sulfide. This 2-step process results in electrically conducting fibers having superior conductivity which is not lost in repeated washings. The touch and other physical characteristics of the starting acrylic fibers are preserved in the process and the electrically conductive fibers can be dyed by cationic dyes. This 2-step method is described and claimed in copending U.S. patent application, Ser. No. 183,639.
It is an object of the present invention to simplify the 2-step (2-bath) method for producing electrically conducting acrylic and acrylic-series fibers while, at the same time, retaining the superior electrical conductivity, hue, touch, washability, dyeing power and other physical properties of the fibers.